Love this topic. I remember Everquest used to checksum areas of memory that were commonly modified from cheats. World of Warcraft used to (possibly still does, it has been forever since I looked at this) inject anti cheat code at runtime.

Obfuscation and deobfuscation is also super interesting. I think overall reverse engineering and figuring out how things work is one of the most interesting things in computer science.

https://github.com/obfuscator-llvm/obfuscator/tree/llvm-4.0/...

https://blog.quarkslab.com/deobfuscation-recovering-an-ollvm...